sound slowing down

[martijn]

Hey Michael,

strangest thing happened the other day:

playing 1 sample, all was OK.
Playing 2 samples, the sound slowed down.

I had the input of my audigy zs nb switched off in asio4all.
When I enabled the input again, the problem was gone.

It might have been that the samples where of a different sample rate.

Eventhough the solution was simple, I wanted to let you know in case it is/was a bug.

grtz Martijn

[Michael Tippach]

The "slowing down" effect you experienced I can only attribute to what would be a constant restarting of the ASIO4ALL engine due to audio buffer underrun at small buffer sizes.

So why would this go away as soon as you enable the inputs?

The answer is that sometimes it does - and this is not just counterintuitive, but also not what the documentation says about inputs - if you do not use them.

I have been able to reproduce this on a number of different audio devices myself.

Due to the design of the audio engine in more recent versions of ASIO4ALL, this is very well explained by the fact, that any new input event is being used to immediately re-fill the output queue again and not wait for the next "output complete" event to get signalled as would be the case in output-only mode.

Especially the input-output-syncronzation has been subject to some very heavy optimization in the recent past, where we probably arrived at a point at which the additional CPU overhead from having the inputs running despite not using them is not as big as to not have that additional triggering source stabilize the output timing.

The real nightmare is to update the documentation so as to convey this factoid to the average newbie user